Apparatus and calculating method of ph

ABSTRACT

A human load of regularly measuring a pH of a position 4 meters from a discharge point during a term of a commissioning of a ship with a scrubber apparatus is reduced. Provided is an apparatus provided inside a ship having a scrubber, including a first pH measuring instrument which measures a pH value of washing water discharged from the scrubber to outboard, a second pH measuring instrument which measures a pH value of washing water supplied from outboard to the scrubber, and a calculating unit which calculates a pH value of water at a predetermined position outboard, based on a dilution ratio which shows a ratio by which the washing water discharged to outboard is diluted at the predetermined position outboard, the pH value measured by the first pH measuring instrument, and the pH value measured by the second pH measuring instrument.

The contents of the following Japanese patent applications areincorporated herein by reference:

-   -   NO. 2015-052204 filed in JP on Mar. 16, 2015    -   NO. PCT/JP2016/53582 filed on Feb. 5, 2016.

BACKGROUND

1. Technical Field

The present invention relates to an apparatus and a calculating methodof pH.

A pH of a sulfur absorbing liquid which is sea water having absorbedsulfur is around 3. In order to discharge the sulfur absorbing liquid tothe sea, the pH must be raised. Conventionally, the pH value has beenraised by exposing the sulfur absorbing liquid in the air in an aerationapparatus (for instance, refer to WO No. 2006/018911).

2. Related Art

A guideline related to environmental regulations when discharging thesea water having absorbed sulfur oxides to the sea is established.According to the guideline MEPC 59/24/Add.1, “During commissioning ofthe exhaust gas cleaning unit(s) after installation, the dischargedwashwater plume should be measured externally from the ship (while beingat anchor) and the discharge pH at the ship's overboard pH monitoringpoint will be recorded when the plume at 4 metres from the dischargepoint equals or is above pH 6.5.” The commissioning at the time ofinstalling the exhaust gas cleaning apparatus extends over several days.During the term of the commissioning, various tests such as changing theengine load and operating the exhaust gas cleaning apparatus areperformed. During the term of the commissioning, it is thought that aperson regularly measures a pH of the position 4 meters from thedischarge point, but a human load of this measuring method is large.

SUMMARY

An apparatus provided inside a ship having a scrubber in a first aspectof the present invention includes a first pH measuring instrument, asecond pH measuring instrument, and a calculating unit. The first pHmeasuring instrument may measure a pH value of washing water dischargedfrom the scrubber to outboard. The second pH measuring instrument maymeasure a pH value of washing water supplied from outboard to thescrubber. The calculating unit may calculate a pH value of water at apredetermined position outboard, based on a dilution ratio which shows aratio by which the washing water discharged to outboard is diluted atthe predetermined position outboard, the pH value measured by the firstpH measuring instrument, and the pH value measured by the second pHmeasuring instrument.

The calculating unit may calculate a value of the dilution ratio inadvance, based on a first pH value measured by the first pH measuringinstrument, a second pH value measured by the second pH measuringinstrument, and a third pH value of the water at the predeterminedposition outboard. The apparatus may further include a recording unit.The recording unit may be connected to the calculating unit. Therecording unit may record the value of the dilution ratio. Thecalculating unit may calculate the pH value of the water at thepredetermined position, based on a pH value measured by the first pHmeasuring instrument after measuring the first pH value, a pH valuemeasured by the second pH measuring instrument after measuring thesecond pH value, and the value of the dilution ratio recorded in therecording unit.

The calculating unit may calculate the dilution ratio, using pH1 whichis the first pH value, pH2 which is the second pH value, and pH3 whichis the third pH value, by

α=(10^(−pH1)−10^(−pH2))/(10^(−pH3)−10^(−pH2)).

The calculating unit may calculate in advance a value of a firstdilution ratio calculated based on the pH1, the pH2, and the pH3 when aflow rate of washing water discharged from the scrubber to outboard is afirst flow rate, and a value of a second dilution ratio calculated basedon the pH1, the pH2, and the pH3 when the flow rate of the washing waterdischarged from the scrubber to outboard is a second flow rate. Therecording unit may record the value of the first dilution ratio and thevalue of the second dilution ratio. The calculating unit may calculatethe pH value of the water at the predetermined position, using the valueof the dilution ratio corresponding to the flow rate of the washingwater discharged from the scrubber to outboard. The recording unit mayrecord and associate the flow rate of the washing water and the value ofthe dilution ratio.

The apparatus may further include a controlling unit. The controllingunit may control a flow rate of washing water supplied to the scrubber,depending on the pH value of the water at the predetermined positioncalculated by the calculating unit. If the flow rate of the washingwater supplied to the scrubber is larger than or equal to apredetermined allowable amount, the controlling unit may control theflow rate of the washing water supplied to the scrubber to be smallerthan or equal to the allowable amount, by decreasing an output of amotor which discharges exhaust gas to the scrubber. Provided that theship is determined to be at anchor, the controlling unit may decreasethe output of the motor which discharges the exhaust gas to thescrubber.

A calculating method of pH of water at a predetermined position outsidea ship having a scrubber in a second aspect of the present inventionincludes measuring a pH value of washing water discharged from thescrubber to outboard, measuring a pH value of washing water suppliedfrom outboard to the scrubber, and calculating the pH value of the waterat the predetermined position outboard, based on a dilution ratio whichshows a ratio by which the washing water discharged to outboard isdiluted at the predetermined position outboard, the pH value measured inthe measuring of the pH value of the washing water discharged from thescrubber to outboard, and the pH value measured in the measuring of thepH value of the washing water supplied from outboard to the scrubber.

The calculating method of pH may be performed at a time of commissioningof the ship having the scrubber. The calculating method of pH mayfurther include, before the calculating of the pH value of the water atthe predetermined position outboard, calculating a value of the dilutionratio in advance, based on a first pH value, a second pH value, and athird pH value, and recording the value of the dilution ratio. The firstpH value may be measured in the measuring of the pH value of the washingwater discharged from the scrubber to outboard. The second pH value maybe measured in the measuring of the pH value of the washing waterdischarged from the scrubber to outboard. The third pH value may be thepH value of the water at the predetermined position outboard. Thecalculating of the pH value of the water at the predetermined positionoutboard may be calculating the pH value of the water at thepredetermined position outboard, based on the pH value of the washingwater discharged from the scrubber to outboard which is measured aftermeasuring the first pH value, the pH value of the washing water suppliedfrom outboard to the scrubber which is measured after measuring thesecond pH value, and the value of the dilution ratio recorded.

The calculating of the value of the dilution ratio in advance may havecalculating a value of a first dilution ratio, and a value of a seconddilution ratio. The value of the first dilution ratio may be calculatedbased on the first pH value, the second pH value, and the third pH valuewhen a flow rate of the washing water discharged from the scrubber tooutboard is a first flow rate. The value of the second dilution ratiomay be calculated based on the first pH value, the second pH value, andthe third pH value when the flow rate of the washing water dischargedfrom the scrubber to outboard is a second flow rate. The recording ofthe value of the dilution ratio may have recording the value of thefirst dilution ratio and the value of the second dilution ratio. Thecalculating method of pH may further include calculating the pH value ofthe water at the predetermined position outboard, using the value of thedilution ratio corresponding to the flow rate of the washing waterdischarged from the scrubber to outboard.

The calculating method of pH may further include controlling a flow rateof the washing water supplied to the scrubber, depending on the pH valuecalculated in the calculating of the pH value of the water at thepredetermined position outboard. The calculating method of pH mayfurther include, if the flow rate of the washing water supplied to thescrubber is larger than or equal to a predetermined allowable amount,decreasing an output of a motor which discharges exhaust gas to thescrubber to control the flow rate of the washing water supplied to thescrubber to be smaller than or equal to the allowable amount. Thecalculating method of pH may further include, provided that the ship isdetermined to be at anchor, decreasing an output of a motor whichdischarges exhaust gas to the scrubber.

The summary clause does not necessarily describe all necessary featuresof the embodiments of the present invention. The present invention mayalso be a sub-combination of the features described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a state of sampling sea water of a position4 meters from a discharge point 86.

FIG. 2 is a diagram showing details of exhaust gas cleaning apparatus50.

FIG. 3 is a flow diagram of a first embodiment in which a pH value at aposition 4 meters from a discharge point 86 is measured using a value ofa single dilution ratio α. FIG. 4 is a flow diagram of a secondembodiment in which a pH value at a position 4 meters from a dischargepoint 86 is measured using values of a plurality of dilution ratios alto an.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, the present invention is described through the embodimentsof the invention. However, the following embodiments do not limit theinvention according to the claims. Also, all the combinations of thefeatures described in the embodiments are not necessarily essential formeans provided by aspects of the invention.

FIG. 1 is a diagram showing a state of sampling sea water of a position4 meters from a discharge point 86. A ship 100 of the present examplehas, at least, exhaust gas cleaning apparatus 50, a main engine 60, achimney 78, an inlet opening 72, an intake pump 74, an outlet opening82, and a discharge pump 84. Note that, the above-described members andportions are merely minimum members and portions necessary fordescribing the characteristics of the ship 100 of the present exampleThe ship 100 may have an element other than the above-described membersand portions. Also, in FIG. 1, an illustration of the part of the ship100 between the bow and the stern is omitted due to limitations of spaceon the sheet of paper.

The main engine 60 as a motor gives a power to a screw of the ship 100.Thereby, the ship 100 obtains a propulsive force. Because heavy oil iscombusted in the main engine 60, exhaust gas is generated. The exhaustgas discharged from the main engine 60 enters a scrubber 10 of theexhaust gas cleaning apparatus 50. Note that, the motor may also haveanother engine other than the main engine 60. In this case, exhaust gasof another engine other than the main engine 60 may also be entered intothe scrubber 10.

The exhaust gas cleaning apparatus 50 of the present example is providedinside the ship 100. The exhaust gas cleaning apparatus 50 has, atleast, a scrubber 10, a first pH measuring instrument 12, and a secondpH measuring instrument 14. The scrubber 10 cleans the exhaust gasdischarged from the main engine 60.

The exhaust gas includes sulfur oxides (SO_(x)) and the like. Thescrubber 10 decreases the concentration of the sulfur oxides in theexhaust gas, by gas-liquid reacting the exhaust gas including the sulfuroxides and the like and the sea water. Thereby, the scrubber 10 cleansthe exhaust gas. The exhaust gas cleaned by the scrubber 10 isdischarged outside the ship 100 through the chimney 78.

The intake pump 74 supplies sea water as washing water to the scrubber10 through the inlet opening 72 from outside the ship 100. The second pHmeasuring instrument 14 measures a pH value of the sea water. Note that,in the present example, the inlet opening 72 is provided at a shipbottom.

The discharge pump 84 discharges sea water as washing water to outsidethe ship 100 through the outlet opening 82 from the scrubber 10. Thefirst pH measuring instrument 12 measures a pH value of the sea waterafter cleaning the exhaust gas. Note that, the outlet opening 82 of thepresent example is provided at a position that the outlet opening 82 isimmersed in sea water. A discharge direction of the outlet opening 82may be a depth direction in sea water.

An operator 92 boards a small ship 90. The operator 92 identifies apredetermined position outside the ship 100 by a surveying instrument94. In the present example, the operator 92 identifies a position at aradius 4 meters from a discharge point 86, by the surveying instrument94. The operator 92 gathers around 500 ml of sea water at the identifiedposition by a sampling container 96. The operator 92 measures a pH valueof the gathered sea water by means already known such as a pH meter.Thereby, a pH value of the sea water at the position 4 meters from adischarge point 86 is acquired.

FIG. 2 is a diagram showing details of exhaust gas cleaning apparatus50. The exhaust gas cleaning apparatus 50 has a scrubber 10, a first pHmeasuring instrument 12, a second pH measuring instrument 14, acalculating unit 20, a recording unit 30, and a controlling unit 40. Thecalculating unit 20, the recording unit 30, and the controlling unit 40may be configured by a general purpose computer, or may also beconfigured by connecting a plurality of modules.

The calculating unit 20 calculates a pH value of water at apredetermined position outboard, based on a dilution ratio a which showsa ratio by which washing water discharged to outboard is diluted at thepredetermined position outboard, a pH value measured by the first pHmeasuring instrument 12, and a pH value measured by the second pHmeasuring instrument 14. Specifically, if the calculating unit 20already has the information of the dilution ratio a, the calculatingunit 20 calculates the pH of the sea water at the position 4 meters fromthe discharge point 86, which is the predetermined position outboard.Regarding this, the description will be specifically made below.

(Calculation of a Single Dilution Ratio α)

A first pH value measured by the first pH measuring instrument 12 and asecond pH value measured by the second pH measuring instrument 14 areinputted to the calculating unit 20. Also, a third pH value of water atthe position 4 meters from a discharge point 86, which is measured bythe operator 92 by the pH meter and the like, is inputted to thecalculating unit 20. The calculating unit 20 calculates in advance avalue of a dilution ratio, based on the first pH value, the second pHvalue, and the third pH value.

Specifically, the calculating unit 20 calculates a dilution ratio α,using a pH1 which is the first pH value, a pH2 which is the second pHvalue, and a pH3 which is the third pH value, by the following[Expression 1].

α=(10^(−pH1)−10^(−pH2))/(10^(−pH3)−10^(−pH2))   [Expression 1]

If the raw water at the concentration C1 is diluted by the dilutionwater at the concentration C2, then, as a result, the raw water becomesat the concentration C3, the dilution ratio a becomes the following[Expression 2].

α=(C1−C2)/(C3−C2)   [Expression 2]

In a case of a hydrogen ion concentration Cn, pHn as the pH valuebecomes the following [Expression 3].

pHn=−log₁₀(Cn)   [Expression 3]

If an expression of the [Expression 3] is variated, it becomes thefollowing [Expression 4].

Cn=10^(−PHn)   [Expression 4]

Regarding n=1,2,3, the [Expression 4] is respectively substituted intothe [Expression 2]. Thereby, it can be understood that the dilutionratio α is expressed like the above [Expression 1].

For instance, if the pH1 measured by the first pH measuring instrument12 is 6.60, the pH2 measured by the second pH measuring instrument 14 is9.00, and the pH3 of the sea water of the position 4 meters from thedischarge point 86 is 8.35, from the [Expression 1], α=72.2. In thespecification, a hydrogen ion concentration of the water which entersthe first pH measuring instrument 12 is expressed by C1, a hydrogen ionconcentration of the water which enters the second pH measuringinstrument 14 is expressed by C2, and a hydrogen ion concentration ofthe sea water of the position 4 meters from the discharge point 86 isexpressed by C3.

(Calculation of pH3)

The recording unit 30 is connected to the calculating unit 20. Therecording unit 30 records a value of the dilution ratio α calculated bythe calculating unit 20. The calculating unit 20 can exchange data withthe recording unit 30. The calculating unit 20 calculates a pH value ofwater at the predetermined position, based on a pH value measured by thefirst pH measuring instrument 12 after measuring the first pH value(pH1), a pH value measured by the second pH measuring instrument 14after measuring the second pH value (pH2), and a value of the dilutionratio cc recorded by the recording unit 30.

From the [Expression 2 ], C3 is expressed by the following [Expression5].

C3=C2+(C1−C2)/α  [Expression 5]

For instance, an amount of the exhaust gas which enters the scrubber 10from the main engine 60 increases, and the pH value measured by thefirst pH measuring instrument 12 and the pH value measured by the secondpH measuring instrument 14 sometimes change. Even in this case, the pHvalue of the sea water of the position 4 meters from the discharge point86 can be calculated using the already known dilution ratio α. Forinstance, because if the pH value measured by the first pH measuringinstrument 12 is 5.60, the pH value measured by the second pH measuringinstrument 14 is 5.60, α=72.2, so, from [Expression 4] and [Expression5], the pH value of the sea water of the position 4 meters from thedischarge point 86 becomes 7.42.

Therefore, the pH value of the sea water of the predetermined positionoutboard can be calculated using the pH values newly measured by thefirst pH measuring instrument 12 and the second pH measuring instrument14 and the already known dilution ratio α. Thereby, if the dilutionratio α is once measured, by sequentially updating the pH values of thefirst pH measuring instrument 12 and the second pH measuring instrument14, pH of the point 4 meters from the discharge point 86 can be known.

(Calculation of a plurality of dilution ratios α1 to αn) Note that,depending on a load of the main engine 60, the flow rate of washingwater discharged from the scrubber 10 to outboard sometimes changes. Itis thought that if the washing water flow rate changes, the dilutionratios a also changes. Therefore, the calculating unit 20 may calculatein advance a plurality of dilution ratios a which respectivelycorrespond to different washing water flow rates. That is, thecalculating unit 20 may calculate in advance a value of a first dilutionratio α1 calculated based on the pH1, the pH2, and the pH3, if a flowrate of washing water discharged from the scrubber 10 to outboard is afirst flow rate. Furthermore, the calculating unit 20 may calculate inadvance a value of a second dilution ratio α2 calculated based on thepH1, the pH2, and the pH3, if a flow rate of washing water dischargedfrom the scrubber 10 to outboard is a second flow rate. Also, therecording unit 30 may record the value of the first dilution ratio andthe value of the second dilution ratio.

The calculating unit 20 may calculate a pH value of water at thepredetermined position, using values al to an of the dilution ratiocorresponding to a flow rate of washing water discharged from thescrubber 10 to outboard. Note that, ‘n’ is a natural number.Furthermore, the recording unit 30 may record and associate the washingwater flow rate and values al to an of the dilution ratio. Thereby, therecording unit 30 may have a table of dilution ratios al to an withrespect to the washing water flow rate.

If the load of the main engine 60 increases, the amount of the exhaustgas increases. It is expected that, if the flow rate of the washingwater supplied to the scrubber 10 is constant, the pH value measured bythe first pH measuring instrument 12 decreases, and the pH value ofwater at the predetermined position outboard also lowers. Then, it issometimes required to increase the flow rate of the washing watersupplied to the scrubber 10, in order to make the pH value of the seawater of the position 4 meters from the discharge point 86 of the outletopening 82 to be larger than or equal to 6.5.

The controlling unit 40 of the present example is connected to thecalculating unit 20 via the recording unit 30. Note that, thecontrolling unit 40 may also be directly connected to the calculatingunit 20. The controlling unit 40 controls flow rate of washing watersupplied to the scrubber 10, depending on a pH value of water at thepredetermined position calculated by the calculating unit 20. Forinstance, if it is expected that, if the washing water flow rate ismaintained constant as it is, the pH value of the sea water of theposition 4 meters from the discharge point 86 falls below 6.5, thecontrolling unit 40 controls the intake pump 74, and increases a flowrate of washing water supplied to the scrubber 10. Note that, if thewashing water flow rate increases, the dilution ratio α rises.

The calculating unit 20 may calculate the smallest washing water flowrate required for the pH value of the sea water of the position 4 metersfrom the discharge point 86 becomes larger than or equal to 6.5, usingthe pH value of the first pH measuring instrument 12, the pH value ofthe second pH measuring instrument 14, and the table of the dilutionratios al to an with respect to the washing water flow rate which aremeasured at any time. Because if the washing water flow rate isincreased, the load of the intake pump 74 increases, the amount ofincrease in the washing water flow rate is preferably the smallest.

In order that the pH value of the sea water of the position 4 metersfrom the discharge point 86 becomes larger than or equal to 6.5, from[Expression 3] and [Expression 5], it is only necessary to satisfy thefollowing [Expression 6].

6.5≦pH=−log₁₀ [C2+(C1−C2)/α]  [Expression 6]

From [Expression 4] and [Expression 6], it is only necessary that thedilution ratio α satisfies the following [Expression 7]. It is onlynecessary that the calculating unit 20 finds the smallest cc whichsatisfies [Expression 7] (that is, the smallest washing water flow rate)from the table of the dilution ratios α1 to αn with respect to thewashing water flow rate.

(10^(−pH1)−10^(−pH2))/(10^(−6.5)−10^(−pH2))≦α  [Expression 7]

The controlling unit 40 may control the intake pump 74 so as to supplywashing water from the intake pump 74 to the scrubber 10, at thesmallest washing water flow rate calculated by the calculating unit 20.Also, the controlling unit 40 may control the scrubber 10 so that thescrubber 10 operates at the washing water flow rate. In this way, if thedilution ratio α is measured in advance every changed washing water flowrate, even if the washing water flow rate changes, the pH at theposition 4 meters from a discharge point 86 can be known withoutmeasuring the dilution ratio α again.

If flow rate of washing water supplied to the scrubber 10 is larger thanor equal to a predetermined allowable amount, the controlling unit 40may also control flow rate of washing water supplied to the scrubber 10to smaller than or equal to the allowable amount, by decreasing anoutput of the main engine 60 as a motor which discharges exhaust gas tothe scrubber 10. In the scrubber 10, there is a limit pressure ofwashing water spray pressure in the scrubber 10, and an upper limit ofwashing water discharging capacity of the scrubber 10. If the washingwater flow rate larger than or equal to the allowable amount of thescrubber 10, which exceeds the limit pressure and the upper limit ofwashing water discharging capacity of the scrubber 10, flows, there is adanger that the scrubber 10 is broken.

Therefore, the controlling unit 40 may control the main engine 60 anddecrease the output of the main engine 60. Thereby, the amount of theexhaust gas from the main engine 60 to the scrubber 10 decreases. Inother words, by making the washing water flow rate to be smaller than orequal to the allowable amount, while complying that the pH value of thesea water of the position 4 meters from the discharge point 86 is largerthan or equal to 6.5, a breakage of the scrubber 10 can be avoided. Notethat, the allowable amount of the washing water flow rate of thescrubber 10 is determined in advance at a time of designing the scrubber10.

The exhaust gas amount emitted from the main engine 60 is an amount thatis in accordance with the load of the main engine 60. The main engine 60is sometimes operated not only for generating a power of the ship 100,but also for generating the electric power necessary for the ship 100.During navigation of the ship 100, it is inconvenient on using the ship100 to be forced to decrease the load of the main engine 60, due to thewashing water flow rate being limited to the allowable amount thewashing water flow rate of the scrubber 10. Therefore, provided that theship 100 is determined to be at anchor, the controlling unit 40 maydecrease an output of the main engine 60 as a motor which dischargesexhaust gas to the scrubber 10. Also, this matches that the pH value ofthe position 4 meters from the discharge point 86 is smaller than orequal to 6.5 is a condition required to the ship 100 at anchor.

FIG. 3 is a flow diagram of a first embodiment in which a pH value at aposition 4 meters from a discharge point 86 is measured using a value ofa single dilution ratio α. Note that, the flow may be performed at atime of commissioning of the ship 100 having the scrubber 10.

(Step S1)

Step S1 is a step of calculating in advance a value of a dilution ratio,based on the first pH value measured in a step of measuring the pH valueof the washing water discharged from the scrubber 10 to outboard usingthe first pH measuring instrument 12, the second pH value obtained bymeasuring the pH value of the washing water supplied from outboard tothe scrubber 10 using the second pH measuring instrument 14, in a stepof measuring the pH value of the washing water discharged from thescrubber 10 to outboard using the first pH measuring instrument 12, andthe third pH value of the water at the predetermined position outboard.Specifically, in Step S1, the calculating unit 20 calculates in advancethe dilution ratio α using the first to third pH values and theabove-described [Expression 1] to [Expression 4].

(Step S2)

Step S2 is a step of recording a value of the dilution ratio α which iscalculated in advance. Specifically, the recording unit 30 records thedilution ratio α calculated in advance by the calculating unit 20.

(Step S3)

Step S3 is a step of measuring a pH value of washing water dischargedfrom the scrubber 10 to outboard, after measuring the first pH value.Specifically, the first pH measuring instrument 12 measures a pH valueof washing water discharged from the scrubber 10 to outboard.Furthermore, the first pH measuring instrument 12 may input the measuredpH value to the calculating unit 20.

(Step S4)

Step S4 is a step of measuring a pH value of washing water supplied fromoutboard to the scrubber 10, after measuring the second pH value.Specifically, the second pH measuring instrument 14 measures a pH valueof washing water supplied from outboard to the scrubber 10. Furthermore,the second pH measuring instrument 14 may input the measured pH value tothe calculating unit 20.

(Step S5)

Step S5 is a step of calculating a pH value of water at thepredetermined position outboard, based on a pH value of washing waterdischarged from the scrubber 10 to outboard which is measured aftermeasuring the first pH value, a pH value of washing water supplied fromoutboard to the scrubber 10 which is measured after measuring the secondpH value, and a value of the dilution ratio cc recorded. Specifically,by substituting values of the dilution ratio α calculated in advance inStep S2, the pH value measured by the first pH measuring instrument 12in Step S3, and the pH value measured by the second pH measuringinstrument 14 in Step S4 into [Expression 4] and [Expression 5], thecalculating unit 20 calculates the pH value of the position 4 metersfrom the discharge point 86. Thereby, if the dilution ratio α is oncemeasured, by sequentially updating the pH values of the first pHmeasuring instrument 12 and the second pH measuring instrument 14, pH ofthe position 4 meters from the discharge point can be known.

(Step S6)

Step S6 is a step of determining whether to repeat Step S3 to Step S5again or not. Specifically, the controlling unit 40 may determinewhether to repeat Step S3 to Step S5 again or not. If YES in Step S6,Step S3 to S5 may be repeated a plurality of times. If NO in Step S6,the flow ends (Step S9).

FIG. 4 is a flow diagram of a second embodiment in which a pH value at aposition 4 meters from a discharge point 86 is measured using values ofa plurality of dilution ratios al to an. Note that, Step S1′, Step S2′,and Step S3′of the present example are different from Step S1, Step S2,and Step S3 of the first embodiment. Also, the present example mayarbitrarily have an additional Step S7. The present example differs fromthe first embodiment in this point. The points other than that arecommon to the first embodiment.

(Step S1′)

Step S1′ of the present example is a step of calculating in advance avalue of the dilution ratio α. In Step S1′, the calculating unit 20calculates a value of a first dilution ratio calculated based on thefirst pH value, the second pH value, and the third pH value, if a flowrate of washing water discharged from the scrubber 10 to outboard is afirst flow rate, and a value of a second dilution ratio calculated basedon the first pH value, the second pH value, and the third pH value, if aflow rate of washing water discharged from the scrubber 10 to outboardis a second flow rate. Note that, in Step S1′ of the present example,the calculating unit 20 may also calculate two or more dilution ratios.That is, the calculating unit 20 may calculate the dilution ratiocorresponding to different washing water flow rates. The dilution ratiosal to an (‘n’ is a natural number) may correspond to first to nth flowrates of washing water flow rates.

(Step S2′)

Step S2′ of the present example is a step in which the recording unit 30records a plurality of dilution ratios α1 to αn. That is, the recordingunit 30 records a table of the dilution ratios al to an with respect tothe washing water flow rate.

(Step S3′) Step S3′ of the present example calculates a pH value ofwater at the predetermined position outboard, using a value of thedilution ratio corresponding to a flow rate of washing water dischargedfrom the scrubber 10 to outboard. Specifically, the calculating unit 20calculates the pH value of water at the position 4 meters from adischarge point 86, using the value of the dilution ratio correspondingto a washing water flow rate, among the dilution ratios α1 to αn. Inthis way, if the dilution ratios a are measured in advance for everychanged washing water flow rate, even if the washing water flow ratechanges, the pH at the point 4 meters from a discharge point 86 can beknown without measuring the dilution ratio α again.

(Step S7)

Step S7 is a step which may be arbitrarily performed. If NO in Step S6,the step advances to Step S7. If YES in Step S6, the step shifts to StepS3′.

Step S7 has a step of controlling flow rate of washing water supplied tothe scrubber 10, depending on a pH value calculated in a step ofcalculating a pH value of water at the predetermined position outboard.Specifically, if it is expected that, if the washing water flow rate ismaintained constant as it is, the pH value of the sea water of theposition 4 meters from the discharge point 86 falls below 6.5, thecontrolling unit 40 controls the intake pump 74, and increases a flowrate of washing water supplied to the scrubber 10.

Also, if flow rate of washing water supplied to the scrubber 10 islarger than or equal to a predetermined allowable amount, Step S7 mayhave a step of decreasing an output of the main engine 60 as a motorwhich discharges exhaust gas to the scrubber 10 and controlling flowrate of washing water supplied to the scrubber 10 to smaller than orequal to the allowable amount. Specifically, the controlling unit 40 maycontrol the main engine 60 and decrease the output of the main engine60. Thereby, by making the washing water flow rate to be smaller than orequal to the allowable amount, while complying that the pH value of thesea water of the position 4 meters from the discharge point 86 is largerthan or equal to 6.5, a breakage of the scrubber 10 can be avoided. Inaddition, provided that the ship 100 is determined to be at anchor, StepS7 may also have a step of decreasing an output of the main engine 60 asa motor which discharges exhaust gas to the scrubber 10.

(Step S8)

Step S8 is a step of determining whether to repeat Step S3′, Step S4,and Step S5 and Step S7, or, only Step S7 again or not. Specifically,the controlling unit 40 may determine which step(s) to be repeated againor not. If YES in Step S8, the step returns to Step S6. Step S3′, StepS4, and Step S5 may be repeated a plurality of times. After that, thestep returns to Step S6 again. If NO in Step S8, the flow ends (StepS9).

While the embodiments of the present invention have been described, thetechnical scope of the invention is not limited to the above-describedembodiments. It is apparent to persons skilled in the art that variousalterations and improvements can be added to the above-describedembodiments. It is also apparent from the scope of the claims that theembodiments added with such alterations or improvements can be includedin the technical scope of the invention.

The operations, procedures, steps, and stages of each process performedby an apparatus, system, program, and method shown in the claims,embodiments, or diagrams can be performed in any order as long as theorder is not indicated by “prior to,” “before,” or the like and as longas the output from a previous process is not used in a later process.Even if the process flow is described using phrases such as “first” or“next” in the claims, embodiments, or diagrams, it does not necessarilymean that the process must be performed in this order.

EXPLANATION OF REFERENCES

10: scrubber,

12: first pH measuring instrument,

14: second pH measuring instrument,

20: calculating unit,

30: recording unit,

40: controlling unit,

50: exhaust gas cleaning apparatus,

60: main engine,

72: inlet opening,

74: intake pump,

78: chimney,

82: outlet opening,

84: discharge pump,

86: discharge point,

90: small ship,

92: operator,

94: surveying instrument,

96: sampling container,

100: ship

What is claimed is:
 1. An apparatus provided inside a ship having ascrubber, comprising: a first pH measuring instrument which measures apH value of washing water discharged from the scrubber to outboard; asecond pH measuring instrument which measures a pH value of washingwater supplied from outboard to the scrubber; and a calculating unitwhich calculates a pH value of water at a predetermined positionoutboard, based on a dilution ratio which shows a ratio by which thewashing water discharged to outboard is diluted at the predeterminedposition outboard, the pH value measured by the first pH measuringinstrument, and the pH value measured by the second pH measuringinstrument.
 2. The apparatus according to claim 1, wherein thecalculating unit calculates a value of the dilution ratio in advance,based on a first pH value measured by the first pH measuring instrument,a second pH value measured by the second pH measuring instrument, and athird pH value of the water at the predetermined position outboard, theapparatus further comprises a recording unit which is connected to thecalculating unit, and records the value of the dilution ratio, and thecalculating unit calculates the pH value of the water at thepredetermined position, based on a pH value measured by the first pHmeasuring instrument after measuring the first pH value, a pH valuemeasured by the second pH measuring instrument after measuring thesecond pH value, and the value of the dilution ratio recorded in therecording unit.
 3. The apparatus according to claim 2, wherein thecalculating unit calculates the dilution ratio, using pH1 which is thefirst pH value, pH2 which is the second pH value, and pH3 which is thethird pH value, byα=(10^(−pH1)−10^(−pH2))/(10^(−pH3)−10^(−pH2)).
 4. The apparatusaccording to claim 3, wherein the calculating unit calculates in advancea value of a first dilution ratio calculated based on the pH1, the pH2,and the pH3 when a flow rate of washing water discharged from thescrubber to outboard is a first flow rate, and a value of a seconddilution ratio calculated based on the pH1, the pH2, and the pH3 whenthe flow rate of the washing water discharged from the scrubber tooutboard is a second flow rate, the recording unit records the value ofthe first dilution ratio and the value of the second dilution ratio, thecalculating unit calculates the pH value of the water at thepredetermined position, using the value of the dilution ratiocorresponding to the flow rate of the washing water discharged from thescrubber to outboard, and the recording unit records and associates theflow rate of the washing water and the value of the dilution ratio. 5.The apparatus according to claim 4 further comprising a controlling unitwhich controls a flow rate of washing water supplied to the scrubber,depending on the pH value of the water at the predetermined positioncalculated by the calculating unit.
 6. The apparatus according to claim5, wherein if the flow rate of the washing water supplied to thescrubber is larger than or equal to a predetermined allowable amount,the controlling unit controls the flow rate of the washing watersupplied to the scrubber to be smaller than or equal to the allowableamount, by decreasing an output of a motor which discharges exhaust gasto the scrubber.
 7. The apparatus according to claim 6, wherein providedthat the ship is determined to be at anchor, the controlling unitdecreases the output of the motor which discharges the exhaust gas tothe scrubber.
 8. A calculating method of pH of water at a predeterminedposition outside a ship having a scrubber, comprising: measuring a pHvalue of washing water discharged from the scrubber to outboard;measuring a pH value of washing water supplied from outboard to thescrubber; and calculating the pH value of the water at the predeterminedposition outboard, based on a dilution ratio which shows a ratio bywhich the washing water discharged to outboard is diluted at thepredetermined position outboard, the pH value measured in the measuringof the pH value of the washing water discharged from the scrubber tooutboard, and the pH value measured in the measuring of the pH value ofthe washing water supplied from outboard to the scrubber.
 9. Thecalculating method of pH according to claim 8 performed at a time ofcommissioning of the ship having the scrubber.
 10. The calculatingmethod of pH according to claim 8, further comprising: before thecalculating of the pH value of the water at the predetermined positionoutboard, calculating a value of the dilution ratio in advance, based ona first pH value measured in the measuring of the pH value of thewashing water discharged from the scrubber to outboard, a second pHvalue measured in the measuring of the pH value of the washing waterdischarged from the scrubber to outboard, and a third pH value of thewater at the predetermined position outboard; and recording the value ofthe dilution ratio, wherein the calculating of the pH value of the waterat the predetermined position outboard is calculating the pH value ofthe water at the predetermined position outboard, based on the pH valueof the washing water discharged from the scrubber to outboard which ismeasured after measuring the first pH value, the pH value of the washingwater supplied from outboard to the scrubber which is measured aftermeasuring the second pH value, and the value of the dilution ratiorecorded.
 11. The calculating method of pH according to claim 10,wherein the calculating of the value of the dilution ratio in advancehas calculating: a value of a first dilution ratio calculated based onthe first pH value, the second pH value, and the third pH value when aflow rate of the washing water discharged from the scrubber to outboardis a first flow rate, and a value of a second dilution ratio calculatedbased on the first pH value, the second pH value, and the third pH valuewhen the flow rate of the washing water discharged from the scrubber tooutboard is a second flow rate, the recording of the value of thedilution ratio has recording the value of the first dilution ratio andthe value of the second dilution ratio, the calculating method of pHfurther comprises calculating the pH value of the water at thepredetermined position outboard, using the value of the dilution ratiocorresponding to the flow rate of the washing water discharged from thescrubber to outboard.
 12. The calculating method of pH according toclaim 8, further comprising controlling a flow rate of the washing watersupplied to the scrubber, depending on the pH value calculated in thecalculating of the pH value of the water at the predetermined positionoutboard.
 13. The calculating method of pH according to claim 12,further comprising: if the flow rate of the washing water supplied tothe scrubber is larger than or equal to a predetermined allowableamount, decreasing an output of a motor which discharges exhaust gas tothe scrubber to control the flow rate of the washing water supplied tothe scrubber to be smaller than or equal to the allowable amount. 14.The calculating method of pH according to claim 12, further comprisingprovided that the ship is determined to be at anchor, decreasing anoutput of a motor which discharges exhaust gas to the scrubber.